boost/simple_segregated_storage won't work (but I can't replicate the failure)

[conversy]

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brew --prefix emscripten/bin/em++ -v build/cookbook/gui/direct_manipulation/simplest/simplest.o -o build/cookbook/gui/direct_manipulation/simplest/simplest_app.html -s USE_SDL=2 -pthread -gsource-map -s USE_SDL=2 -s FULL_ES3 -s MIN_WEBGL_VERSION=2 -s MAX_WEBGL_VERSION=2 -s ASSERTIONS=2 -s NO_DISABLE_EXCEPTION_CATCHING -s ERROR_ON_UNDEFINED_SYMBOLS=1 -s PTHREAD_POOL_SIZE=5 -L../../misc/emscripten/local-install/lib -s USE_SDL=2 -pthread -gsource-map -s USE_SDL=2 -s FULL_ES3 -s MIN_WEBGL_VERSION=2 -s MAX_WEBGL_VERSION=2 -s ASSERTIONS=2 -s NO_DISABLE_EXCEPTION_CATCHING -s ERROR_ON_UNDEFINED_SYMBOLS=1 -s PTHREAD_POOL_SIZE=5 -L../../misc/emscripten/local-install/lib -L../djnn-cpp/build/lib -ldjnn-utils -ldjnn-gui -ldjnn-display -ldjnn-base -ldjnn-exec_env -ldjnn-core
/opt/homebrew/Cellar/emscripten/3.1.61/libexec/llvm/bin/clang --version
/opt/homebrew/Cellar/emscripten/3.1.61/libexec/llvm/bin/wasm-ld -o build/cookbook/gui/direct_manipulation/simplest/simplest_app.wasm build/cookbook/gui/direct_manipulation/simplest/simplest.o -L../../misc/emscripten/local-install/lib -L../../misc/emscripten/local-install/lib -L../djnn-cpp/build/lib ../djnn-cpp/build/lib/libdjnn-utils.a ../djnn-cpp/build/lib/libdjnn-gui.a ../djnn-cpp/build/lib/libdjnn-display.a ../djnn-cpp/build/lib/libdjnn-base.a ../djnn-cpp/build/lib/libdjnn-exec_env.a ../djnn-cpp/build/lib/libdjnn-core.a -L/opt/homebrew/Cellar/emscripten/3.1.61/libexec/cache/sysroot/lib/wasm32-emscripten /opt/homebrew/Cellar/emscripten/3.1.61/libexec/cache/sysroot/lib/wasm32-emscripten/libSDL2-mt.a /opt/homebrew/Cellar/emscripten/3.1.61/libexec/cache/sysroot/lib/wasm32-emscripten/crtbegin.o -lGL-mt-webgl2-full_es3-getprocaddr -lal -lhtml5 -lbulkmemory -lstubs-debug -lnoexit -lc-mt-debug -ldlmalloc-mt-debug -lcompiler_rt-mt -lc++-mt -lc++abi-debug-mt -lsockets-mt -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-cxx-exceptions -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr /var/folders/_y/mk1ljg908xj95w0059blfnxr0000gp/T/tmpld89c5idlibemscripten_js_symbols.so --import-memory --shared-memory --export=emscripten_stack_get_end --export=emscripten_stack_get_free --export=emscripten_stack_get_base --export=emscripten_stack_get_current --export=emscripten_stack_init --export=_emscripten_stack_alloc --export=_emscripten_thread_free_data --export=_emscripten_thread_crashed --export=emscripten_main_runtime_thread_id --export=emscripten_main_thread_process_queued_calls --export=_emscripten_run_on_main_thread_js --export=emscripten_stack_set_limits --export=__get_temp_ret --export=__set_temp_ret --export=__cxa_is_pointer_type --export=__cxa_can_catch --export=__cxa_increment_exception_refcount --export=__cxa_decrement_exception_refcount --export=setThrew --export=__cxa_free_exception --export=__wasm_call_ctors --export=_emscripten_tls_init --export=_emscripten_thread_init --export=_emscripten_stack_restore --export=_emscripten_thread_exit --export=__get_exception_message --export=free --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export-if-defined=__start_em_lib_deps --export-if-defined=__stop_em_lib_deps --export-if-defined=__start_em_js --export-if-defined=__stop_em_js --export-if-defined=main --export-if-defined=__main_argc_argv --export-if-defined=fflush --export-table -z stack-size=65536 --no-growable-memory --initial-memory=16777216 --no-entry --stack-first --table-base=1
"/opt/homebrew/opt/[email protected]/bin/python3.12" -E /opt/homebrew/Cellar/emscripten/3.1.61/libexec/tools/wasm-sourcemap.py build/cookbook/gui/direct_manipulation/simplest/simplest_app.wasm --dwarfdump=/opt/homebrew/Cellar/emscripten/3.1.61/libexec/llvm/bin/llvm-dwarfdump -o build/cookbook/gui/direct_manipulation/simplest/simplest_app.wasm.map --basepath=/Users/conversy/recherche/istar/code/djnn/smala/build/cookbook/gui/direct_manipulation/simplest
/opt/homebrew/Cellar/emscripten/3.1.61/libexec/llvm/bin/llvm-objcopy build/cookbook/gui/direct_manipulation/simplest/simplest_app.wasm build/cookbook/gui/direct_manipulation/simplest/simplest_app.wasm --remove-section=.debug* --remove-section=producers
/opt/homebrew/Cellar/emscripten/3.1.61/libexec/binaryen/bin/wasm-emscripten-finalize -g --dyncalls-i64 --pass-arg=legalize-js-interface-exported-helpers --check-stack-overflow --dwarf --output-source-map-url=simplest_app.wasm.map build/cookbook/gui/direct_manipulation/simplest/simplest_app.wasm -o build/cookbook/gui/direct_manipulation/simplest/simplest_app.wasm --detect-features --input-source-map=build/cookbook/gui/direct_manipulation/simplest/simplest_app.wasm.map --output-source-map=build/cookbook/gui/direct_manipulation/simplest/simplest_app.wasm.map
/opt/homebrew/opt/node/bin/node /opt/homebrew/Cellar/emscripten/3.1.61/libexec/src/compiler.mjs /var/folders/_y/mk1ljg908xj95w0059blfnxr0000gp/T/tmpzgzr1wi6.json
/opt/homebrew/opt/node/bin/node /opt/homebrew/Cellar/emscripten/3.1.61/libexec/tools/preprocessor.mjs /var/folders/_y/mk1ljg908xj95w0059blfnxr0000gp/T/emscripten_temp_ke3ux0zh/settings.js shell.html

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This function: https://github.com/boostorg/pool/blob/ec7da07ed13e0c61e50d945b574a12ae7ec83cf4/include/boost/pool/simple_segregated_storage.hpp#L91
seems to sometimes fail with emscripten.

    static void * & nextof(void * const ptr)
    { //! The return value is just *ptr cast to the appropriate type. ptr must not be 0. (For the sake of code readability :)
    //! As an example, let us assume that we want to truncate the free list after the first chunk.
    //! That is, we want to set *first to 0; this will result in a free list with only one entry.
    //! The normal way to do this is to first cast first to a pointer to a pointer to void,
    //! and then dereference and assign (*static_cast<void **>(first) = 0;).
    //! This can be done more easily through the use of this convenience function (nextof(first) = 0;).
    //! \returns dereferenced pointer.
      return *(static_cast<void **>(ptr));
    }

The problem is: I can't replicate the failure with this simple program (which is a simple adaptation of my real code):

//#define BOOST_POOL_VALIDATE
#include <boost/pool/simple_segregated_storage.hpp>
#include <assert.h>

//char cmap [256 * (2 * sizeof(float))];
float pool [256 * 2];

unsigned int 
allocate_coords_plain(boost::simple_segregated_storage<size_t>& alloc, size_t num)
{
    if (num%4) num += 4-num%4; // align to 4

    //auto cmap = pool;
    char* const cmap = (char*) pool;

    auto mem = (char*) alloc.malloc_n(num/4, 4 * (2 * sizeof(float)));
    assert(mem >= cmap);
 
    unsigned int result = (mem - cmap) / (2 * sizeof(float));
    return result;
}

int main()
{
    boost::simple_segregated_storage<size_t> alloc;
    alloc.add_ordered_block((float*)pool, 256 * (2 * sizeof(float)), 4 * (2 * sizeof(float)));

    for (size_t i=0; i<16; ++i) {
        auto mem = allocate_coords_plain (alloc, 4);
        printf("%d\n", mem);
    }

    return 0;
}

This simple program works with emscripten.
In my real code, it returns 0.

Does someone know of any possible reason why this code would fail?

Best,

Stéphane

[sbc100]

Likely some kind of memory corruption issue. You could try ASan (-fsanitize=address).

[conversy]

@sbc100 thank you for the tip. I check with -fsanitize=address regularly.

Using regular c++, there is no problem with -fsanitize=address.
With emscripten, I get an Uncaught RuntimeError: memory access out of bounds, when I try to allocate some memory from the pool...

It's in boost::simple_segregated_storage<unsigned long>::try_malloc_n(void*&, unsigned long, unsigned long) here: https://github.com/boostorg/pool/blob/ec7da07ed13e0c61e50d945b574a12ae7ec83cf4/include/boost/pool/simple_segregated_storage.hpp#L326